Production of caoutchouc threads



July 26, 1938. H. SCHULLER :rAL 2,124,637

PRODUCTION OF CAOUTCHOUC THREADS Filed Aug. 14, 191 55 Patented July 26, 1938 PATENT OFFICE PRODUCTION OF CAOUTCHOUC THREADS Hans Schiiller, Emil Matzrfer, and Armand Kailich, Vienna, Austria, assignors to United States Rubber Products, Inc., New York, N. Y., a corporation of Delaware Application August 14, 1935, Serial No. 36,146 In Austria September 20, 1934 13 Claims.

Processes for the production of cao'utchouc threads are known, in which the threads are formed by i'ntertwisting orby twisting caoutchouc bands of suitable width. Processes of this kind for the production of caoutchouc threads are also known, in which from caoutchouc solutions, dispersions or the like, preferably from aqueous caoutchouc dispersions, caoutchouc strips or hands are formed directly in a width corresponding to the threads to be made and these strips or bands are twisted to form round or approximately round threads. It is also known to subject such bands, while the surface is still in a sticky state, that is as soon as possible after consolidation, to a twisting process, so that the convolutions at the same time become stuck together.

The invention is based on the observation, that the angles at which the band is twisted are of considerable importance for the formation of the thread, since by these angles both the pitch of the helical winding of the band to form a thread and consequently the properties of the thread, such as strength to resist tearing, extensibility and the like and also by the shape of the thread, can be influenced.

In the accompanying drawing the process according to the invention is diagrammatically illustrated in several constructional examples, wherein- Figs. 1 and 1 illustrate in side elevation two examples of the way in which the band is drawn off or the angle of twist is given to the thread;

Figs. 2, 2 and 2 illustrate in front elevation several examples of the way in which the band may be drawn oif at a transverse angle to the general direction of movement of the thread;

Figs. 3 and 4 show an elevation and a transverse section, respectively, of a helical thread according to the present invention.

As angles of twisting there are mainly two angles of importance:

1. The longitudinal angle, that is the angle (a) between the tangential plane of the support at the point where the thread is formed (P) and the direction of the formed thread structure travelling to the twisting apparatus (4) v 2. The-transverse angle, that is the angle (p) between the thread structure travelling to the twisting apparatus (4) and a plane which can be erected at the point where the thread is formed (P) through the longitudinal axis of the band lying on the support, perpendicular to the support. According to' the invention it has been ascertained that for the pitch of the convolutions and consequently for the elasticity and strength to resist tearing of the thread the more important angle is the longitudinal angle andfor the geometrical form the more important angle is the transverse angle. The thread will become more extensible as the pitch of the convolutions decreases, but will be less capable of withstanding tearing; whereas it will become less extensible but will have greater strength to .resist tearing the greater the pitch of the convolutions. Thus, according to whether more extensible or stronger threads are to be made, the pitch of the formed thread must in the first case be influenced by the selection of a suitably large longitudinal angle and in the second case, by the selection of a suitably small longitudinal angle. The smaller the longitudinal angle, the greater 'will be the pitch of the convolutions of the band, threads with a practically infinitely great pitch of twist being produced, when the longitudinal angle is equal to zero or approximately equal to zero.

Obviously by a suitable choice of longitudinal angle all desired intermediate stages as regards the pitch of the convolutions and consequently as regards the elasticity or strength, can be obtained.

On the other hand, by the selection of a correspondingly great transverse angle, a perfectly round, cylindrical and smooth thread may be obtained, the mechanical properties of which may be regulated by the longitudinal angle employed at the same time. When the transverse angle lies below a certain range which for diiferent rubber qualities is different and is also dependent on the apparatus used, an uneven, mostly more or less oval thread will in general be obtained. The cross section of the thread will be the flatter, the smaller the transverse angle becomes. If, however, a transverse angle differing only slightly or not at all from the zero value be combined with a longitudinal angle which is very small or equal to zero, the latter being for instance obtained by the rubber band being drawn off at a point of the support, at which the latter is curved or from a roller or cylinder interposed between the support and the twisting apparatus, this will result in a thread such as that shown in Fig. 3 in elevation and in Fig. 4 in cross section; the twisting preferably being effected by means of a twisting device which can exert on the thread during the twisting operation a pinching or squeezing effect, as for instance a twisting device which consists of rolls 6 which are pressed against one another and rotated in opposite directions and are adapted to receive the thread between them, said rolls being supported by a frame I which is rotatable by means ofa pulley 8. Such a thread has the form of a band twisted to a helical line. Owing to the mode of manufacture of the thread by twisting a thin rubber strip, this band shows an insertion in textile goods, since, owing to its special form, it cannot shift or can only shift with difliculty in the woven or knitted fabric, so that with such a thread any slipping out or forming of loops projecting from the textile product is avoided.

No definite values can be given for themost favourable angles of twist (a+p) in each case, as for these angles not only the composition of the rubber mixture, solution or dispersion used is determining, but also the intended degree of the final effect. Thus, for instance, for making a helical thread, such as that of- Figs. 3 and 4, the angles oftwist it and 8 must not be exactly equal to zero, but must only be suitably small. If the transverse angle be gradually increased, the helical form will approach nearer and nearer to the form of the round. thread, finally merging into the latter, while a completely round thread In the process according to the invention the formation of the thread takes place obviously in-the following manner:

. The smaller the longitudinal angle, the great--' er will be the longitudinal tension and pitch with which the rubber band is twisted in mutually overlapping helical convolutions to form a thread. Owing to this longitudinal tension of the rubber band, all the helical convolutions of the crosssection of the thread have the tendency to become narrower, whereby they are continuously firmly pressed against one another and thus become firmly stuck together, which must result in an increased tensile strength of the thread. On the other-hand, the elasticity or extensibility of the thread is slightly decreased through the large pitch of the helical convolutions, similarly to the case of a helical spring of large pitch.

As regards the transverse angle, this angle influences the thread formation in the geometrical respect, the effect being such that, for instance with a large transverse angle, the helical 'windings will always wrap positively only about one edge of the rubber band as the core while, the

so that in the subsequent twisting a fiat core is formed from the first and consequently afiat cross section of the thread.

If to this fiat shape-there be added through the simultaneous application of a very small longithe of the direction of twist'helically over the surface of the flat thread, the flat thread, after having left the twisting apparatus, will contract helically in the sense opposite to that of the direction of twist and will permanently retain this form (helical thread). Actually in such a helical thread the inner convolutions and the outer helical line run in opposite directions.

The process according to the invention may be carried out continuously and with a plurality of supports or rubber bands and also, for instance, in such a manner that the band (strip or the like) to be twisted is drawn off the support, on which it is formed, and is directly twisted or that the band is drawn oif the support, on which it is formed, by a drawing-off device and is only then twisted. A suitable drawing-off device for the process according to the invention is for'instance a roller which may be driven at a corresponding speed, a a pair of rollers, or the like.

The rubber band 2 which is formed on the support I is drawn off by a twisting device 4 at the point P under the longitudinal anglea and the transverse angle 5 from the support I, with or without the interposition of a roller 5 (Fig. 1) and is twisted to form a thread 3.

The intermediate roller 5 (Fig. 1") may either be driven itself or turn loosely on a shaft. In the former case the drawing off of the rubber band from the support is effected by the roller, while in the second case this must be eflected by the twisting device.

Such a drawing ofi device, formed for instance by an intermediate roller 5, has the effect that the thread is formed not on the support I, on which the film 2 has been formed, but on the drawing off device at P.

Through the interposition of such a drawi off, device on the path of the band as it comes from the support on which it is formed to the twisting device, a thread forming point P is ob,- tained, which always remains constant, whereas,

when the film is taken directly from the supporting band, fluctuations in the drawing of! point which, in this case is at the same time the point P where the thread is formed, areunavoidable, which fluctuations may lead to variations in the longitudinal angle or in the pitch and consequently to changes in the mechanical properties of the formed thread.

Such a drawing-off device provides the further advantage, that the band to be twisted is accessible on its way to the twistingdevice and can easily be influenced as regardsits properties, for

instance its physical properties, by suitable treatment.

Figs. 1' and 2 show the rubber band to be twisted being drawn ofi at a point on the support, at which the latter is passing over a curved guide in a tangential direction to this curvature, that is, with a longitudinal angle a=0; and Figs. 1, 2 and 2 show the film being drawn off by means of an intermediate roller at a longitudinal angle (i=0; Fig. 2 showing the employment of a transverse-angle 5:0 and'Fig. 2 the employment of a transverse angle ,6 which is greater than zero- The previous example,.showing the drawing off of the thread can of course also be carried out with the angle 5:0.

1. A process for the production of caoutchouc threads which comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawn oif from a curved part of a supporting surface in a direction substantially tangential to the said curved part.

2. A process for the production of caoutchouc threads which comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawn ofi from a rotating drum in a direction approximately tangential thereto.

3. The process according to claim 1, wherein the thin band of caoutchouc is in a tacky condition while it is being subjected to the twisting.

operation.

4. The process according to claim 2, wherein the thin band of caoutchouc is in a tacky condition while it is being subjected to the twisting operation.

5. A process for the production of caoutchouc threads which comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawn oif from a rotating drum in a direction approximately tangential thereto and at a transverse angle to the direction of general movement of the drum.

6. A process for the production of caoutchouc threads which comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawnoif from a curved part of a supporting surface in a directiomsubstantially tangential to said curved part, as well as in a direction transverse to the direction of general movement of said support.

7. The process according to claim 5, wherein the thin band of caoutchouc is in a tacky condition while it is being subjected to the twisting operation.

8. A process for the production ofcaoutchouc threads which comprises forming a thin band of caoutchouc upon a movingsupporting surface, withdrawing said formed band from said moving surface and causing it to pass over a rotating drum, withdrawing said band from the drum in a direction tangential thereto and simultaneously subjecting it to a twisting operation.

9. A process for the production of caoutchouc threads which comprises forming a thin band of caoutchouc upon a, moving supporting surface, withdrawing said formed band from said moving surface and causing it to pass over a rotating drum, withdrawing said band from the drum in a direction tangential thereto and at a transverse angle to the direction of general movement of said rotating drum and simultaneously subjecting it to a twisting operation.

10. A process for the production of caoutchouc threads with a helically shaped surface which comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawn ofi from a curved part of a supporting surface in a direction substantially tangential to said surface and in the direction of the general movement of said support.

11. A process according to claim 10 in which the thread is subjected to a squeezing pressure.

12. A process for the production of caoutchouc threads with a helically shaped surface which v comprises subjecting a thin band of caoutchouc to a twisting operation while it is being drawn off from a rotating drum in a direction approximately tangential thereto and in the direction of the general movement of said rotating drum.

13. A process according to claim 12, in which the thread is subjected to a squeezing pressure.

' HANS EMIL MA'IZNER.

ARMAND KAILICH. 

